U.S. patent application number 13/001561 was filed with the patent office on 2011-05-05 for nitrile group-containing highly saturated copolymer rubber.
Invention is credited to Shinya Ikeda, Kiyonori Umetsu, Tsutomu Yoshimura.
Application Number | 20110105692 13/001561 |
Document ID | / |
Family ID | 41444593 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110105692 |
Kind Code |
A1 |
Yoshimura; Tsutomu ; et
al. |
May 5, 2011 |
NITRILE GROUP-CONTAINING HIGHLY SATURATED COPOLYMER RUBBER
Abstract
A nitrile group-containing highly saturated copolymer rubber
having .alpha.,.beta.-ethylenically unsaturated nitrile monomer
units (a) and conjugated diene monomer units (b) and having at
least part of said conjugated diene monomer units (b) hydrogenated,
wherein a content of said .alpha.,.beta.-ethylenically unsaturated
nitrile monomer units (a) is 37 to 45 wt %, a total of said
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
and said conjugated diene monomer units (b) is 93 wt % or more, an
iodine value is 9 or less, and a half value width of a peak of a
loss tangent (tan.delta.) in the viscoelastic properties when made
into a cross-linked product is 5 to 20.degree. C. in range.
Inventors: |
Yoshimura; Tsutomu; (Tokyo,
JP) ; Umetsu; Kiyonori; (Tokyo, JP) ; Ikeda;
Shinya; (Tokyo, JP) |
Family ID: |
41444593 |
Appl. No.: |
13/001561 |
Filed: |
June 26, 2009 |
PCT Filed: |
June 26, 2009 |
PCT NO: |
PCT/JP2009/061694 |
371 Date: |
December 27, 2010 |
Current U.S.
Class: |
525/328.3 |
Current CPC
Class: |
C08C 19/02 20130101;
C08F 236/12 20130101; C08K 5/14 20130101; C08L 15/005 20130101;
C08F 2/001 20130101; C08K 5/14 20130101; C08F 236/12 20130101 |
Class at
Publication: |
525/328.3 |
International
Class: |
C08F 8/04 20060101
C08F008/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2008 |
JP |
2008-168641 |
Claims
1. A nitrile group-containing highly saturated copolymer rubber
having .alpha.,.beta.-ethylenically unsaturated nitrile monomer
units (a) and conjugated diene monomer units (b) and having at
least part of said conjugated diene monomer units (b) hydrogenated,
wherein a content of said .alpha.,.beta.-ethylenically unsaturated
nitrile monomer units (a) is 37 to 45 wt %, a total of said
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
and said conjugated diene monomer units (b) is 93 wt % or more, an
iodine value is 9 or less, and a half value width of a peak of a
loss tangent (tan.delta.) in the viscoelastic properties when made
into a cross-linked product is 5 to 20.degree. C. in range.
2. The nitrile group-containing highly saturated copolymer rubber
as set forth in claim 1, wherein the ratio of content of said
conjugated diene monomer units (b) is 48 to 63 wt %.
3. A cross-linkable rubber composition containing the nitrile
group-containing highly saturated copolymer rubber as set forth in
claim 1 and a cross-linking agent.
4. The cross-linkable rubber composition as set forth in claim 3
wherein said cross-linking agent is an organic peroxide.
5. A rubber cross-linked product obtained by cross-linking the
cross-linkable rubber composition as set forth in claim 3.
6. The rubber cross-linked product as set forth in claim 5 which is
a part used in contact with oil.
7. A method of production of the nitrile group-containing highly
saturated copolymer rubber as set forth in claim 1 comprising the
step of: starting copolymerization by using 90 to 99 wt % of the
total amount of the monomers when making the total amount of the
monomers used for copolymerization as 100 wt %, additionally adding
the balance of the total amount of the monomers used for
copolymerization, when a polymerization conversion rate reaches 40
to 90%, to obtain the copolymer, and then selectively hydrogenating
the copolymer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a nitrile group-containing
highly saturated copolymer rubber, more particularly relates to a
nitrile group-containing highly saturated copolymer rubber able to
give a cross-linked product excellent in ordinary properties and
heat resistance and superior in oil resistance.
BACKGROUND ART
[0002] A nitrile group-containing highly saturated copolymer rubber
represented by a hydrogenated acrylonitrile-butadiene copolymer
rubber is superior in heat resistance, oil resistance, ozone
resistance, etc. compared with a general nitrile group-containing
copolymer rubber high in a ratio of carbon-carbon unsaturated bonds
in its main chain structures such as an acrylonitrile-butadiene
copolymer rubber.
[0003] However, depending on the content of nitrile groups and
ratio of unsaturated bonds in carbon-carbon bonds in the nitrile
group-containing highly saturated copolymer rubber, the cold
resistance was sometimes inferior to that of a nitrile
group-containing copolymer rubber. Further, recently, much better
improvement has been sought in the oil resistance.
[0004] As opposed to this, to improve the cold resistance of a
nitrile group-containing highly saturated copolymer rubber, for
example, Patent Document 1 proposes a nitrile group-containing
highly saturated copolymer rubber comprising
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units,
.alpha.,.beta.-ethylenically unsaturated carboxylic acid ester
monomer units, conjugated diene monomer units, and saturated
conjugated diene monomer units in predetermined ratios and having a
temperature difference of an extrapolated glass transition
initiating temperature (Tig) and an extrapolated glass transition
end temperature (Teg) in differential scan calorimetry of not more
than 10.degree. C.
[0005] However, the nitrile group-containing highly saturated
copolymer rubber described in Patent Document 1 is superior in cold
resistance, but when used as belts used in contact with oil (for
example, belts for use as automobile parts) etc., the oil
resistance is not necessarily sufficient in view of the recent
tougher levels demanded. Therefore, further improvement of the oil
resistance has been desired.
[0006] Prior Art Documents
[0007] Patent Documents
[0008] Patent Document 1: Japanese Patent Publication (A) No.
2001-114940 (Specification of U.S. Pat. No. 6,548,604)
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0009] The present invention has as its object to provide a nitrile
group-containing highly saturated copolymer rubber able to give a
cross-linked product excellent in ordinary properties and heat
resistance and superior in oil resistance. Further, the present
invention has as its object to provide a cross-linkable rubber
composition comprised of the nitrile group-containing highly
saturated copolymer rubber to which a cross-linking agent is added
and a rubber cross-linked product obtained by cross-linking the
cross-linkable rubber composition.
Means for Solving the Problems
[0010] The inventors etc. engaged in intensive research to solve
the above problems and as a result discovered that a nitrile
group-containing highly saturated copolymer rubber containing
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
and conjugated diene monomer units (b) in predetermined ratios and
having a half value width of a peak of a loss tangent (tan.delta.)
in viscoelastic properties when made into a cross-linked product of
a range of 5 to 20.degree. C. enables the objects to be achieved
and thereby completed the present invention.
[0011] That is, according to the present invention, there is
provided a nitrile group-containing highly saturated copolymer
rubber having .alpha.,.beta.-ethylenically unsaturated nitrile
monomer units (a) and conjugated diene monomer units (b) and having
at least part of the conjugated diene monomer units (b)
hydrogenated, wherein a content of the .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) is 37 to 45 wt %, a total of
the .alpha.,.beta.-ethylenically unsaturated nitrile monomer units
(a) and the conjugated diene monomer units (b) is 93 wt % or more,
an iodine value is 9 or less, and a half value width of a peak of a
loss tangent (tan.delta.) in the viscoelastic properties when made
into a cross-linked product is 5 to 20.degree. C. in range.
[0012] In the nitrile group-containing highly saturated copolymer
rubber of the present invention, preferably the ratio of content of
the conjugated diene monomer units (b) is 48 to 63 wt %.
[0013] Further, according to the present invention, there is
provided a cross-linkable rubber composition containing the above
nitrile group-containing highly saturated copolymer rubber and a
cross-linking agent.
[0014] In the cross-linkable rubber composition of the present
invention, preferably the cross-linking agent is an organic
peroxide.
[0015] Furthermore, according to the present invention, there is
provided a rubber cross-linked product obtained by cross-linking
the above cross-linkable rubber composition. The rubber
cross-linked product of the present invention is preferably used as
a part used in contact with oil.
[0016] According to the present invention, there is provided a
method of production of the above nitrile group-containing highly
saturated copolymer rubber comprising the step of: starting
copolymerization by using 90 to 99 wt % of the total amount of the
monomers when making the total amount of the monomers used for
copolymerization as 100 wt %, additionally adding the balance of
the total amount of the monomers used for copolymerization, when a
polymerization conversion rate reaches 40 to 90%, to obtain the
copolymer, and then selectively hydrogenating the copolymer.
EFFECTS OF THE INVENTION
[0017] According to the present invention, it is possible to
provide a nitrile group-containing highly saturated copolymer
rubber able to give a cross-linked product excellent in ordinary
properties and heat resistance and superior in oil resistance, and
a rubber cross-linked product obtained by cross-linking this having
excellent ordinary properties and heat resistance, and superior oil
resistance.
EMBODIMENTS CARRYING OUT THE INVENTION
[0018] Nitrile Group-Containing Highly Saturated Copolymer
Rubber
[0019] The nitrile group-containing highly saturated copolymer
rubber of the present invention has .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) and conjugated diene monomer
units (b), has at least part of the conjugated diene monomer units
(b) hydrogenated, has a ratio of content of the
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
of 37 to 45 wt %, has a total of the .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) and the conjugated diene
monomer units (b) of 93 wt % or more, has an iodine value of 9 or
less, and has a half value width of a peak of a loss tangent
(tan.delta.) in viscoelastic properties when made into a
cross-linked product of 5 to 20.degree. C. in range.
[0020] The monomer forming the .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) is not particularly limited
so long as an .alpha.,.beta.-ethylenically unsaturated compound
having nitrile groups. Acrylonitrile; .alpha.-chloroacrylonitrile,
.alpha.-bromoacrylonitrile, and other
.alpha.-halogenoacrylonitriles; methacrylonitrile,
ethacrylonitrile, and other .alpha.-alkylacrylonitriles; etc. may
be mentioned. Among these as well, acrylonitrile and
methacrylonitrile are preferable. As the
.alpha.,.beta.-ethylenically unsaturated nitrile monomer, a
plurality of types of these may also be jointly used.
[0021] In the nitrile group-containing highly saturated copolymer
rubber, the ratio of content of the .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) is, in the total monomer
units, 37 to 45 wt %, preferably 38 to 42 wt %, particularly
preferably 39 to 41 wt %. Making the ratio of content of the
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
in the above range, a cross-linked product superior in oil
resistance and cold resistance and having a half value width of a
peak of a loss tangent (tan.delta.) of 5 to 20.degree. C. in range
can be easily obtained.
[0022] As the conjugated diene monomer forming the conjugated diene
monomer units (b), 1,3-butadiene, isoprene,
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. may be mentioned.
Among these, 1,3-butadiene is preferable.
[0023] In the nitrile group-containing highly saturated copolymer
rubber, the ratio of content of the conjugated diene monomer units
(b) is, in the total monomer units, preferably 48 to 63 wt %, more
preferably 51 to 62 wt %, particularly preferably 59 to 61 wt %.
Note that, the conjugated diene monomer units (b), at least
partially, preferably in 97 to 99.8 wt % with respect to the total
amount of the conjugated diene monomer units (b) are contained in
the hydrogenated state in the nitrile group-containing highly
saturated copolymer rubber. The above ratio of content is the ratio
including also the conjugated diene monomer units (b) contained in
the hydrogenated state. If the ratio of content of the conjugated
diene monomer units (b) is too small, the obtained rubber
cross-linked product is liable to fall in elasticity. On the other
hand, if too great, the obtained rubber cross-linked product may be
impaired in oil resistance, heat aging resistance, chemical
resistant stability, etc.
[0024] Further, in the nitrile group-containing highly saturated
copolymer rubber, the ratio of content of the total of the
.alpha.,.beta.-ethylenically unsaturated nitrile monomer units (a)
and the conjugated diene monomer units (b) is, in the total monomer
units, 93 wt % or more, preferably 95 wt % or more, more preferably
98 to 100 wt %. If the ratio of content is too small, the obtained
rubber cross-linked product sometimes falls in oil resistance. Note
that, the ratio of content of the total of these is the ratio
including also the conjugated diene monomer units (b) contained in
the hydrogenated state.
[0025] Further, the nitrile group-containing highly saturated
copolymer rubber may also contain units of other monomers able to
copolymerize with the monomers forming .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units (a) and conjugated diene monomer
units (b). As the monomers forming the other copolymerizable
monomer units, for example, .alpha.,.beta.-ethylenically
unsaturated carboxylic acid ester monomers,
.alpha.,.beta.-ethylenically unsaturated carboxylic acid monomers,
.alpha.,.beta.-ethylenically unsaturated polyvalent carboxylic acid
anhydride monomers, aromatic vinyl monomers, fluorine-containing
vinyl monomers, copolymerizable antiaging agents, etc. may be
mentioned.
[0026] As the .alpha.,.beta.-ethylenically unsaturated carboxylic
acid ester monomers, for example, methyl acrylate, butyl acrylate,
n-dodecyl acrylate, methyl methacrylate, and other acrylic acid
alkyl esters and methacrylic acid alkyl esters which have 1 to 18
carbon atoms in the alkyl groups; methoxymethyl acrylate,
methoxyethyl methacrylate, and other acrylic acid alkoxyalkyl
esters and methacrylic acid alkoxyalkyl esters which have 2 to 12
carbon atoms in the alkoxyalkyl groups; .alpha.-cyanoethyl
acrylate, cyanobutyl methacrylate, and other acrylic acid
cyanoalkyl esters and methacrylic acid cyanoalkyl esters which have
2 to 12 carbon atoms in the cyanoalkyl groups; 2-hydroxyethyl
acrylate, 2-hydroxyethyl methacrylate, and other acrylic acid
hydroxyalkyl esters and methacrylic acid hydroxyalkyl esters which
have 1 to 12 carbon atoms in the hydroxyalkyl groups; fluorobenzyl
acrylate, fluorobenzyl methacrylate, and other fluorine-substituted
benzyl group-containing acrylic acid esters and
fluorine-substituted benzyl group-containing methacrylic acid
esters; trifluoroethyl acrylate, tetrafluoropropyl methacrylate,
and other fluoroalkyl group-containing acrylic acid esters and
fluoroalkyl group-containing methacrylic acid esters; dimethyl
maleate, dimethyl fumarate, and other unsaturated polyvalent
carboxylic acid polyalkyl esters; dimethylaminomethyl acrylate and
other amino group-containing .alpha.,.beta.-ethylenically
unsaturated carboxylic acid esters; etc. may be mentioned.
[0027] As the .alpha.,.beta.-ethylenically unsaturated carboxylic
acid monomers, for example, acrylic acid, methacrylic acid, and
other .alpha.,.beta.-ethylenically unsaturated monocarboxylic
acids; maleic acid, fumaric acid, itaconic acid, and other
.alpha.,.beta.-ethylenically unsaturated polyvalent carboxylic
acids; monomethyl maleate, mono n-butyl maleate, and other maleic
acid monoalkyl esters, monocyclohexyl maleate and other maleic acid
monocycloalkyl esters, monomethylcyclopentyl maleate and other
maleic acid monoalkylcycloalkyl esters, monomethyl fumarate, mono
n-butyl fumarate, and other fumaric acid monoalkyl esters,
monocyclopentyl fumarate and other fumaric acid monocycloalkyl
esters, monoethylcyclohexyl fumarate and other fumaric acid
monoalkylcycloalkyl esters, mono n-butyl citraconate and other
citraconic acid monoalkyl esters, monocyclohexyl citraconate and
other citraconic acid monocycloalkyl esters, monomethylcyclopentyl
citraconate and other citraconic acid monoalkylcycloalkyl esters,
monomethyl itaconate, mono n-butyl itaconate, and other itaconic
acid monoalkyl esters, monocyclopentyl itaconate and other itaconic
acid monocycloalkyl esters, monoethylcyclohexyl itaconate and other
itaconic acid monoalkylcycloalkyl esters and other partial esters
of .alpha.,.beta.-ethylenically unsaturated polyvalent carboxylic
acids etc. may be mentioned.
[0028] As .alpha.,.beta.-ethylenically unsaturated polyvalent
carboxylic acid anhydride monomers, for example, maleic anhydride
etc. may be mentioned.
[0029] As aromatic vinyl monomers, styrene, .alpha.-methyl styrene,
vinyl pyridine, etc. may be mentioned.
[0030] As fluorine-containing vinyl monomers, fluoroethylvinyl
ether, o-trifluoromethyl styrene, etc. may be mentioned.
[0031] As copolymerizable antiaging agents,
N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)methacrylamide,
N-(4-anilinophenyl)cinnamamide, N-(4-anilinophenyl)crotonamide,
N-phenyl-4-(3-vinylbenzyloxy)aniline, N-phenyl-4-(4-vinyl
benzyloxy)aniline, etc. may be mentioned.
[0032] As other copolymerizable monomers, a plurality of types may
be jointly used. When including units of these other
copolymerizable monomers, the ratio of content in the nitrile
group-containing highly saturated copolymer rubber is, in the total
monomer units, preferably 7 wt % or less, more preferably 5 wt % or
less, furthermore preferably 2 wt % or less.
[0033] Note that when making the nitrile group-containing highly
saturated copolymer rubber of the present invention into a rubber
part used in contact with oil (for example, a belt used as an
automobile part etc.), to improve the obtained rubber cross-linked
product in oil resistance, it is preferable that a monomer having
carboxylic acid ester groups or carboxyl groups is not used as a
copolymer monomer. When including units of such a monomer having
carboxylic acid ester groups or carboxyl groups (for example, an
.alpha.,.beta.-ethylenically unsaturated carboxylic acid ester
monomer or .alpha.,.beta.-ethylenically unsaturated carboxylic acid
monomer, .alpha.,.beta.-ethylenically unsaturated polyvalent
carboxylic acid anhydride monomer), the ratio of content is
preferably made, in the total monomer units, 5 wt % or less.
[0034] The nitrile group-containing highly saturated copolymer
rubber of the present invention has an iodine value of not more
than 9. If the iodine value is too high, the obtained rubber
cross-linked product is liable to drop in heat aging resistance and
ozone resistance.
[0035] Further, the nitrile group-containing highly saturated
copolymer rubber of the present invention has a half value width of
a peak of a loss tangent (tan.delta.) in viscoelastic properties
when made into a cross-linked product of 5 to 20.degree. C. in
range, preferably 10 to 17.degree. C. in range, more preferably 12
to 15.degree. C. in range. By making the half value width of the
peak of the loss tangent (tan.delta.) in the viscoelastic
properties when made into a cross-linked product the above range,
the obtained rubber cross-linked product can be improved in oil
resistance while being excellent in ordinary properties and heat
resistance.
[0036] The half value width of the peak of the loss tangent
(tan.delta.) in the viscoelastic properties when made into a
cross-linked product can for example be measured under the
following conditions. That is, it is possible to measure the
viscoelasticity under conditions of a measurement frequency of 10
Hz, a static strain of 0.5%, a dynamic strain of 0.2%, and a rate
of temperature rise of 3.degree. C./min using a viscoelasticity
measurement device. Note that, when measuring the viscoelastic
properties when made into a cross-linked product, it is also
possible that the nitrile group-containing highly saturated
copolymer rubber into which the later mentioned cross-linking agent
and compounding agents used when preparing a cross-linkable rubber
composition are suitably mixed is used to obtain a cross-linked
product and the measurement for viscoelastic properties is
performed by using the obtained cross-linked product.
[0037] The nitrile group-containing highly saturated copolymer
rubber of the present invention has a Mooney viscosity
[ML.sub.1+4(100.degree. C.)] of preferably 10 to 120, more
preferably 30 to 110, particularly preferably 40 to 80. If the
Mooney viscosity is too low, the obtained rubber cross-linked
product is liable to fall in mechanical properties. On the other
hand, if too high, the processability may fall when adding a
cross-linking agent to obtain a cross-linkable rubber
composition.
[0038] Method of Production of Nitrile Group-Containing Highly
Saturated Copolymer Rubber
[0039] The method of production of the nitrile group-containing
highly saturated copolymer rubber of the present invention is not
particularly limited, but it is preferable to use emulsion
polymerization using an emulsifier to copolymerize the
above-mentioned monomers and prepare a latex of the nitrile
group-containing copolymer rubber, then hydrogenate this. At the
time of emulsion polymerization, it is possible to use an
emulsifier, polymerization initiator, molecular weight adjuster,
and other normally used secondary materials for polymerization.
[0040] The emulsifier is not particularly limited, but for example,
a polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether,
polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester,
or other nonionic emulsifier; a salt of myristic acid, palmitic
acid, oleic acid, linolenic acid, or other salt of fatty acid,
sodium dodecylbenzene sulfonate or other alkylbenzene sulfonate,
higher alcohol sulfuric acid ester salt, alkylsulfosuccinate, or
other anionic emulsifier; .alpha.,.beta.-unsaturated carboxylic
acid sulfo ester, .alpha.,.beta.-unsaturated carboxylic acid
sulfate ester, sulfoalkylaryl ether, or other copolymerizable
emulsifier; etc. may be mentioned.
[0041] The amount of the emulsifier used, with respect to the total
monomer as 100 parts by weight, is preferably 0.1 to 10 parts by
weight.
[0042] The polymerization initiator is not particularly limited so
long as a radical initiator, but potassium persulfate, sodium
persulfate, ammonium persulfate, potassium perphosphate, hydrogen
peroxide, or other inorganic peroxide; t-butyl peroxide, cumen
hydroperoxide, p-mentane hydroperoxide, di-t-butyl peroxide,
t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide,
octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl
peroxide, t-butylperoxyisobutyrate, or other organic peroxides;
azobis isobutyronitrile, azobis-2,4-dimethylvaleronitrile,
azobiscyclohexane carbonitrile, methyl azobis isobutyrate, and
other azo compounds etc. may be mentioned. These polymerization
initiators may be used alone or in combinations of two or more
types. As the polymerization initiator, an inorganic or organic
peroxide is preferable.
[0043] When using a peroxide as the polymerization initiator, it is
possible to combine it with sodium hydrogen sulfite, ferrous
sulfate, or another reducing agent for use as a redox-type
polymerization initiator.
[0044] The amount of the polymerization initiator used is, with
respect to the total monomers as 100 parts by weight, preferably
0.01 to 2 parts by weight.
[0045] The molecular weight adjuster is not particularly limited,
but t-dodecylmercaptan, n-dodecylmercaptan, octyl mercaptan, or
other mercaptans; carbon tetrachloride, dichloromethane,
dibromomethane, or other halogenated hydrocarbons;
.alpha.-methylstyrene dimer; tetraethyl thiuram disulfide,
dipentamethylene thiuram disulfide, diisopropyl xanthogenate
disulfide, and other sulfur-containing compounds etc. may be
mentioned. These may be used alone or in combinations of two or
more types. Among these, mercaptans are preferable and
t-dodecylmercaptan is more preferable.
[0046] The amount of the molecular weight adjuster used is, with
respect to the total monomers as 100 parts by weight, preferably
0.1 to 0.8 part by weight.
[0047] For the medium of the emulsion polymerization, usually water
is used. The amount of the water is, with respect to the total
monomers as 100 parts by weight, preferably 80 to 500 parts by
weight.
[0048] At the time of the emulsion polymerization, furthermore, in
accordance with need, a stabilizer, dispersant, pH adjuster,
deoxidizer, particle size adjuster, or other secondary materials
for polymerization may be used. When using these, their types and
amounts of use are not particularly limited either.
[0049] In the present invention, when producing the nitrile
group-containing highly saturated copolymer rubber, when making the
total amount of the monomers used for the copolymerization as 100
wt %, first, 90 to 99 wt % in the total amount of monomers is used
to start the copolymerization, then, when the polymerization
conversion rate reaches 40 to 90%, the balance of the monomers to
be used for the copolymerization (that is, 1 to 10 wt %) is
additionally added to thereby obtain the copolymer. Further, when
making the total amount of the monomers as 100 wt %, it is
preferable to use a monomer forming .alpha.,.beta.-ethylenically
unsaturated nitrile monomer units for 37 to 53 wt %. By adopting
this method, it is possible to control the half value width of the
peak of the loss tangent (tan.delta.) in viscoelastic properties to
the above range.
[0050] Note that, the ratio of the monomers used at the time of the
start of copolymerization is 90 to 99 wt % of the total amount of
the monomers, preferably 92 to 98 wt %. That is, the ratio of the
monomers added in the middle of the copolymerization is 1 to 10 wt
% of the total amount of the monomers, preferably 2 to 8 wt %. By
controlling the ratio of the monomers used at the time of the start
of copolymerization and the monomers added in the middle of the
copolymerization, it is possible to control the half value width of
the peak of the loss tangent (tan.delta.) in the viscoelastic
properties to a predetermined range.
[0051] Further, the timing of addition of the monomers additionally
added in the middle of the copolymerization is the timing when the
polymerization conversion rate reaches 40 to 90%, preferably
reaches 50 to 80%, more preferably reaches 55 to 75%. Further, when
additionally adding monomers in the middle of the copolymerization,
they may be added divided into several batches. For example, when
adding them divided into two batches, the first batch is preferably
added when the polymerization conversion rate reaches 20 to 50% and
the second batch is preferably added when the polymerization
conversion rate reaches 50 to 70%.
[0052] Further, it is possible to produce the nitrile
group-containing highly saturated copolymer rubber of the present
invention by selectively hydrogenating the obtained copolymer. Note
that, the type and amount of the hydrogenation catalyst used for
the hydrogenation and hydrogenation temperature etc. may be
determined based on known methods.
[0053] Cross-Linkable Rubber Composition
[0054] The cross-linkable rubber composition of the present
invention contains the above nitrile group-containing highly
saturated copolymer rubber and a cross-linking agent.
[0055] The cross-linking agent used in the present invention is not
particularly limited so long as one which can cross-link the
nitrile group-containing highly saturated copolymer rubber of the
present invention, but preferably a sulfur cross-linking agent or
organic peroxide cross-linking agent etc. may be mentioned.
[0056] As the sulfur cross-linking agent, powdered sulfur,
precipitated sulfur, or other sulfur; 4,4'-dithiomorpholine or
tetramethyl thiuram disulfide, tetraethyl thiuram disulfide,
polymer polysulfide, or other organic sulfur compounds; etc. may be
mentioned. The amount of the sulfur cross-linking agent used, with
respect to the nitrile group-containing highly saturated copolymer
rubber as 100 parts by weight, is preferably 0.1 to 5 parts by
weight, more preferably 0.2 to 4.5 parts by weight, more preferably
0.3 to 4 parts by weight. In the case of using a sulfur
cross-linking agent, if the amount used is too small, the
cross-linking density falls and the obtained cross-linked product
tends to become larger in compression set. On the other hand, if
too great, the obtained cross-linked product becomes insufficient
in bending fatigue resistance or the dynamic heat generation
becomes higher in some cases.
[0057] The organic peroxide cross-linking agent is not particularly
limited so long as one used in the rubber industry as a
cross-linking agent, but dialkyl peroxides, diacyl peroxides,
peroxy esters, etc. may be mentioned. Preferably, dialkyl peroxides
etc. may be illustrated.
[0058] As the dialkyl peroxides, for example, dicumyl peroxide,
di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane,
1,3-bis(t-butylperoxyisopropyl)benzene, etc. may be mentioned.
[0059] As diacyl peroxides, for example, benzoyl peroxide,
isobutyryl peroxide, etc. may be mentioned.
[0060] As peroxy esters, for example,
2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyisopropyl
carbonate, etc. may be mentioned.
[0061] The amount of the organic peroxide cross-linking agent used,
with respect to the nitrile group-containing highly saturated
copolymer rubber as 100 parts by weight, is preferably 1 to 16
parts by weight, more preferably 1 to 14 parts by weight,
furthermore preferably 1 to 12 parts by weight. In the case of
using an organic peroxide cross-linking agent, if the amount used
is too small, the cross-linking density falls and the obtained
cross-linked product tends to become larger in compression set. On
the other hand, if the amount of the organic peroxide cross-linking
agent used is too great, the obtained cross-linked product
sometimes becomes insufficient in rubber elasticity.
[0062] When using a sulfur cross-linking agent as the cross-linking
agent, as a cross-linking aid, it is preferable to jointly use zinc
white, a guanidine-based cross-linking accelerator, a
thiazole-based cross-linking accelerator, a thiuram-based
cross-linking accelerator, a dithiocarbamate-based cross-linking
accelerator, etc.
[0063] Further, when using an organic peroxide cross-linking agent
as the cross-linking agent, as a cross-linking aid, it is possible
to jointly use triallyl cyanurate, trimethylolpropane
trimethacrylate, N,N'-m-phenylene bismaleimide, etc.
[0064] The cross-linking aid may be used alone or may be used in a
combination of a plurality of types. It may also be used dispersed
in clay, calcium carbonate, silica, etc. to improve the
processability for the rubber composition. The amount of the
cross-linking aid used is not particularly limited and may be
determined in accordance with the application and required
performance of the cross-linked product, type of the cross-linking
agent, type of the cross-linking aid, etc.
[0065] Further, the cross-linkable rubber composition of the
present invention may have blended into it, in addition to the
nitrile group-containing highly saturated copolymer rubber and
cross-linking agent and the cross-linking aid and cross-linking
accelerator added in accordance with need, compounding agents
usually used in the rubber field such as, carbon black, silica, or
other reinforcing fillers, calcium carbonate, clay, or other
nonreinforcing fillers, processing aids, plasticizers,
antioxidants, antiozonants, coloring agents, etc. The amounts of
these compounding agents used are not particularly limited so long
as in a range not obstructing the object or effects of the present
invention. Amounts in accordance with the object of compounding may
be compounded.
[0066] The cross-linkable rubber composition of the present
invention may also have rubber other than the nitrile
group-containing highly saturated copolymer rubber of the present
invention blended into it. The blendable rubber is not particularly
limited, but for example when blending a highly unsaturated nitrile
group-containing copolymer rubber such as an
acrylonitrile-butadiene copolymer rubber, the amount blended is
made, with respect to the nitrile group-containing highly saturated
copolymer rubber of the present invention as 100 parts by weight,
30 parts by weight or less, preferably 20 parts by weight or less,
more preferably 10 parts by weight or less. When blending a highly
unsaturated nitrile group-containing copolymer rubber, if the
amount blended is too large, the obtained cross-linked product will
tend to drop in air pressure heat aging resistance, bending fatigue
resistance, elongation, and compression set resistance. Note that,
when blending rubber other than the nitrile group-containing highly
saturated copolymer rubber of the present invention, it is possible
to add the necessary amount of a cross-linking agent able to
cross-link these rubber.
[0067] The cross-linkable rubber composition of the present
invention may be prepared by the method of preparation of general
rubber compositions in the same way as other rubber compositions.
An internal mixer or an open roll etc. may be used for kneading.
When blending a cross-linking agent or a cross-linking aid, after
blending the cross-linking agent or cross-linking aid, the
temperature is adjusted to become less than the cross-linking start
temperature so that cross-linking will not occur during kneading in
the same way as the method of preparation of general cross-linkable
rubber compositions. Usually, a rubber composition not containing
the cross-linking agent, cross-linking aid, etc. is prepared, then
the ingredients relating to cross-linking are blended and mixed at
less than the cross-linking start temperature based.
[0068] Rubber Cross-Linked Product
[0069] The rubber cross-linked product of the present invention is
one obtained by cross-linking the above cross-linkable rubber
composition of the present invention.
[0070] The method of cross-linking the cross-linkable rubber
composition is not particularly limited, but the temperature at the
time of cross-linking is preferably made 100 to 200.degree. C.,
more preferably 130 to 180.degree. C. If the temperature at the
time of cross-linking is too low, the cross-linking time required
becomes too long and the obtained rubber cross-linked product
sometimes falls in cross-linking density. If the temperature at the
time of cross-linking is too high, molding defects sometimes
occur.
[0071] Further, the cross-linking time differs depending on the
cross-linking method, cross-linking temperature, shape of the
cross-linked product, etc., but from the viewpoints of the
cross-linking density of the obtained cross-linked product and
production efficiency is preferably 1 minute to 5 hours in range.
The method of heating for cross-linking may be suitably selected
from press heating, steam heating, oven heating, hot air heating,
or other method used for cross-linking of rubber.
[0072] The rubber cross-linked product of the present invention
obtained in this way is one obtained using the above-mentioned
nitrile group-containing highly saturated copolymer rubber of the
present invention, so has a half value width of a peak of a loss
tangent (tan.delta.) in viscoelastic properties of 5 to 20.degree.
C. in range, maintains good ordinary properties and heat
resistance, and has superior oil resistance.
[0073] Further, this rubber cross-linked product of the present
invention can be suitably used, making use of its characteristics,
for parts used in contact with oil, for example, timing belts and
other belts submersed in oil.
[0074] Alternatively, the cross-linked product of the present
invention can be used, other than for belts submersed in oil, for
O-rings, packings, diaphragms, oil seals, shaft seals, bearing
seals, mechanical seals, well head seals, electrical and electronic
equipment seals, air compressor seals, seals for sealing the
chlorofluorocabon or fluorohydrocarbons or carbon dioxide used for
cooling apparatuses of air-conditioners or compressors for cooling
machines for air-conditioning systems, seals for sealing
supercritical carbon dioxide or subcritical carbon dioxide used for
washing media for precision washing, seals for roller devices
(roller bearings, automobile hub units, automobile water pumps,
linear guide devices, balls and screws, etc.), valves and valve
seats, BOP (Blow Out Preventers), platters, and other various types
of seal materials; and intake manifold gaskets attached at
connecting part of intake manifold and cylinder head, cylinder head
gaskets attached at connecting part of cylinder block and cylinder
head, rocker cover gaskets attached at connecting part of rocker
cover and cylinder head, oil pan gaskets attached at connecting
part of oil pan and cylinder block or transmission case, fuel cell
separator gaskets attached between a pair of housings sandwiching a
unit cell provided with an anode, electrolyte plates, and cathode,
top cover gaskets of hard disk drive, and other various types of
gaskets; printing rolls, ironmaking rolls, papermaking rolls,
industrial use rolls, office machinery rolls, and other various
types of rolls; fuel hoses, turbo air hoses, oil hoses, radiator
hoses, heater hoses, water hoses, vacuum brake hoses, control
hoses, air-conditioner hoses, brake hoses, power steering hoses,
air hoses, marine hoses, risers, flowlines, and other various types
of hoses; CVJ boots, propeller shaft boots, constant velocity joint
boots, rack and pinion boots, and other various types of boots;
cushion materials, dynamic dampers, rubber couplings, air springs,
vibration isolators, and other damping material rubber parts; dust
covers, car interior members, tires, covered cables, shoe soles,
electromagnetic wave shields, flexible printed circuit board
binders and other binders, fuel cell separators, and other broad
applications in the fields of cosmetics and pharmaceuticals, fields
coming into contact with food, the electronics field, etc.
EXAMPLES
[0075] Below, the present invention will be explained based on more
detailed examples, but the present invention is not limited to
these examples. Note that, below, "parts" are based on weight so
long as not indicated otherwise. Further, the tests and evaluations
were performed below.
[0076] Viscoelasticity Test (Half Value Width of Peak of
Tan.delta.)
[0077] A rubber composition for viscoelasticity test use prepared
by the following method was press-formed using a mold at
170.degree. C. for 20 minutes while applying pressure to obtain a
width 10 mm, length 50 mm, thickness 2.15 mm cross-linked product
for viscoelasticity test use. Further, the obtained cross-linked
product for viscoelasticity test use was measured by a
viscoelasticity measurement device (Explexor 500N, made by GABO
QUALIMETER Testanlagen GmbH) under conditions of a measurement
frequency: 10 Hz, static strain: 0.5%, dynamic strain: 0.2%,
measurement temperature range: -50 to 100.degree. C., temperature
elevation rate: 3.degree. C./min, chuck distance: 30 mm,
measurement mode: tension mode.
[0078] Next, a viscoelasticity temperature-tan.delta. chart was
prepared. The temperature at the low temperature side giving a
strength of half of the peak value the Tan.delta. of the chart was
made the temperature of the initiating point, the temperature at
the high temperature side giving a strength of half of the peak
value the Tan.delta. of the chart was made the temperature of the
end point, and the absolute value of difference between temperature
of the end point and temperature of the initiating point was made
the half value width. Note that when the tan.delta. value deviates
between the initiating point and end point, a baseline is drawn and
used for calculating the half value width.
[0079] Iodine Value
[0080] Measured in accordance with JIS K 6235.
[0081] Mooney Viscosity (Polymer Mooney)
[0082] Measured in accordance with JIS K6300-1. Units are
(ML.sub.1+4, 100.degree. C.).
[0083] Oil Resistance Test
[0084] A cross-linkable rubber composition prepared by the
following method was press-formed using a mold at 170.degree. C.
for 20 minutes while applying pressure to obtain a length 20 mm,
width 10 mm, thickness 2 mm sheet-shaped cross-linked product.
Further, in accordance with JIS K6258, the obtained cross-linked
product was immersed in 150.degree. C. engine oil (Genuine Castle
Oil SM/GF-40W-20, made by Toyota) for 168 hours, measured for
volume before and after immersion, and measured for change in
volume .DELTA.V (unit: %).
[0085] Heat Resistance
[0086] Sheet-shaped rubber cross-linked products the same as those
used for evaluation in the above oil resistance tests were punched
into JIS No. 3 dumbbell cutter to prepare test pieces. The obtained
test pieces were used in accordance with the provisions of JIS
K6257 "Aging Test Methods for Vulcanized Rubber", Section 4 "Air
Pressure Heat Aging Test (Normal Oven Method)" for accelerated
aging under conditions of 150.degree. C. and 504 hours and measured
for elongation at break before and after the accelerated aging. The
rate of change of the elongation at break due to the accelerated
aging (units: %) was calculated.
[0087] Ordinary Properties (Tensile Strength, 100% Tensile
Stress)
[0088] Sheet-shaped rubber cross-linked products the same as those
used for evaluation in the above oil resistance tests were punched
into JIS No. 3 dumbbell cutter to prepare test pieces. Further, the
obtained test pieces were used in accordance with JIS K6251 to
measure tensile strength and 100% tensile stress of the rubber
cross-linked products.
Example 1
Production of Latex of Nitrile Copolymer Rubber
[0089] A reactor was charged with an emulsifier of potassium oleate
in 2 parts, a stabilizer of potassium phosphate in 0.1 part, and
water in 150 parts. To this, acrylonitrile in 52 parts,
1,3-butadiene in 48 parts, and a molecular weight adjuster of
t-dodecylmercaptan in 0.45 part were added. Further, an activator
of ferrous sulfate in 0.015 part and a polymerization initiator of
p-menthane hydroperoxide in 0.05 part were added. Emulsion
polymerization was started in the presence of these under
conditions of 10.degree. C. After the start of polymerization, when
the polymerization conversion rate became 65%, 1,3-butadiene in 2
parts were additionally added. Next, when the polymerization
conversion rate reached 80%, 0.2 part of hydroxylamine sulfate was
added per 100 parts of the monomer to stop the polymerization.
Further, after stopping polymerization, the solution was warmed and
steam distilled under reduced pressure at 70.degree. C. to recover
the unreacted monomer, then an antiaging agent of alkylated phenol
in 2 parts was added to thereby obtain a latex of nitrile copolymer
rubber.
[0090] Further, preparing a coagulating solution in 3000 parts in
which coagulating agent of calcium chloride in 3 parts was
dissolved, this was held at 50.degree. C. Into this coagulating
solution, the latex of the nitrile copolymer rubber obtained above
was added dropwise to cause the nitrile copolymer rubber to
coagulate and obtain crumbs. Next, the obtained crumbs were rinsed,
then dried at 50.degree. C. under reduced pressure to prepare a
nitrile copolymer rubber.
[0091] Next, the obtained nitrile copolymer rubber was dissolved in
methylisobutyl ketone and a palladium/silica catalyst was used to
cause a hydrogenation reaction in a pressure vessel at a hydrogen
pressure of 5 MPa, 50.degree. C., and 6 hours to thereby prepare a
nitrile group-containing highly saturated copolymer rubber.
[0092] Further, the above obtained nitrile group-containing highly
saturated copolymer rubber was measured for ratios of contents of
monomer units by .sup.1H-NMR and measured for iodine value.
[0093] Further, the obtained nitrile group-containing highly
saturated copolymer rubber was used to obtain a rubber composition
for a viscoelasticity test as follows.
[0094] That is, to the obtained nitrile group-containing highly
saturated copolymer rubber in 100 parts, zinc white in 5 parts,
substituted diphenylamine (antiaging agent, made by Uniroyal,
Nauguard 445) in 1.5 parts, 2-mercaptobenzoimidazole zinc salt
(antiaging agent, made by Ouchi Shinko Chemical Industrial, Nocrac
MBZ) in 1.5 part, and 1,3-bis(t-butylperoxyisopropyl)benzene
(organic peroxide) 40% product (made by Hercules Inc., Vul-cup
40KE) in 7 parts were mixed and kneaded to obtain a rubber
composition for viscoelasticity test use.
[0095] Further, separate from the above, the obtained nitrile
group-containing highly saturated copolymer rubber was used to
obtain a cross-linkable rubber composition as follows.
[0096] That is, to the nitrile group-containing highly saturated
copolymer rubber in 100 parts, zinc white in 5 parts, stearic acid
in 1 part, SRF carbon black (made by Asahi Carbon, Asahi #50) in 70
parts, a plasticizer (Adekasizer C-8, made by ADEKA) in 5 parts,
substituted diphenylamine (antiaging agent, made by Uniroyal,
Nauguard 445) in 1.5 parts, 2-mercaptobenzoimidazole zinc salt
(antiaging agent, made by Ouchi Shinko Chemical Industrial, Nocrac
MBZ) in 1.5 parts, and 1,3-bis(t-butylperoxyisopropyl)benzene
(organic peroxide) 40% product (made by Hercules Inc., Vul-cup
40KE) in 7 parts were mixed and kneaded to obtain a cross-linkable
rubber composition.
[0097] The rubber composition for viscoelastic tests obtained by
the above was used to measure the viscoelasticity and the
cross-linkable rubber composition was used to evaluate an oil
resistance test, heat resistance test, and ordinary properties
(tensile strength, 100% tensile stress). The results are shown in
Table 1.
Example 2
[0098] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 40 parts and 1,3-butadiene in 60 parts, changing
the monomer added in the middle from 1,3-butadiene in 2 parts to
1,3-butadiene in 3 parts, and changing the timing of addition in
the middle to a polymerization conversion rate 67%, the same
procedure was followed as in Example 1 to prepare a nitrile
group-containing highly saturated copolymer rubber and
cross-linkable rubber composition. These were evaluated in the same
way as Example 1. The results are shown in Table 1.
Example 3
[0099] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 45 parts and 1,3-butadiene in 55 parts, changing
the monomer added in the middle from 1,3-butadiene in 2 parts to
1,3-butadiene in 5 parts, and changing the timing of addition in
the middle to a polymerization conversion rate 67%, the same
procedure was followed as in Example 1 to prepare a nitrile
group-containing highly saturated copolymer rubber and
cross-linkable rubber composition. These were evaluated in the same
way as Example 1. The results are shown in Table 1.
Comparative Example 1
[0100] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 63 parts and 1,3-butadiene in 37 parts and
changing the monomer added in the middle from 1,3-butadiene in 2
parts to 1,3-butadiene in 4 parts, the same procedure was followed
as in Example 1 to prepare a nitrile group-containing highly
saturated copolymer rubber and cross-linkable rubber composition.
These were evaluated in the same way as Example 1. The results are
shown in Table 1.
Comparative Example 2
[0101] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 25 parts and 1,3-butadiene in 75 parts and
changing the monomer added in the middle from 1,3-butadiene in 2
parts to acrylonitrile in 4 parts, the same procedure was followed
as in Example 1 to prepare a nitrile group-containing highly
saturated copolymer rubber and cross-linkable rubber composition.
These were evaluated in the same way as Example 1. The results are
shown in Table 1.
Comparative Example 3
[0102] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 44 parts and 1,3-butadiene in 56 parts and not
adding any monomer in the middle, the same procedure was followed
as in Example 1 to prepare a nitrile group-containing highly
saturated copolymer rubber and cross-linkable rubber composition.
These were evaluated in the same way as Example 1. The results are
shown in Table 1.
Comparative Example 4
[0103] Except for using as the monomers for advance polymerization,
instead of acrylonitrile in 52 parts and 1,3-butadiene in 48 parts,
acrylonitrile in 9 parts, 1,3-butadiene in 47 parts, and butyl
acrylate in 13 parts and changing the monomer added in the middle
from 1,3-butadiene in 2 parts to acrylonitrile in 10 parts,
1,3-butadiene in 10 parts, and butyl acrylate in 10 parts, the same
procedure was followed as in Example 1 to prepare a nitrile
group-containing highly saturated copolymer rubber and
cross-linkable rubber composition. These were evaluated in the same
way as Example 1. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 1 2 3 4
Monomers used at time of start of polymerization Acrylonitrile
(parts by weight) 52 40 45 63 25 44 9 1,3-butadiene (parts by
weight) 48 60 55 37 75 56 47 Butylacrylate (parts by weight) 0 0 0
0 0 0 13 Monomers added in middle Acrylonitrile (parts by weight)
-- -- -- -- 4 -- 10 1,3-butadiene (parts by weight) 2 3 5 4 -- --
10 Butylacrylate (parts by weight) -- -- -- -- -- -- 10 Iodine
value (%) 8 8 8 8 8 8 8 Polymerization conversion rate at addition
in middle (%) 65 67 67 65 65 -- 65 Final polymerization conversion
rate (%) 80 80 80 80 80 80 80 Nitrile group-containing highly
saturated copolymer rubber Acrylonitrile units (wt %) 44 37 40 50
25 40 20 1,3-butadiene units (wt %) 56 63 60 50 75 60 60
Butylacrylate units (wt %) -- -- -- -- -- -- 20 Initiating point of
half value width of peak of tan .delta. (.degree. C.) -7.8 -13.4
-11.0 -3.0 -23.0 -15.3 -18.0 End point of half value width of peak
of tan .delta. (.degree. C.) 11.3 0.4 5.1 17.0 -5.0 8.3 -8.0 Half
value width temperature of peak of tan .delta. (.degree. C.) 19.1
13.8 16.1 20.0 18.0 23.6 10.0 Polymer Mooney viscosity ML.sub.1+4
(100.degree. C.) 70 64 70 73 76 64 75 Cross-linked product Oil
resistance .DELTA.V (150.degree. C. .times. 168 hr) (%) -1.0 +1.7
+1.0 -1.5 +7.0 +1.5 +6.5 Heat resistance (150.degree. C. .times.
504 hr) (%) -42 -17 -29 -60 -30 -60 -30 Tensile strength (MPa) 25
22 23 27 22 23 21 100% tensile stress (MPa) 7.7 5.9 5.6 9.1 4.6 5.5
4.4
[0104] In Table 1, the "initiating point of half value width of
peak of tan.delta." means the point at the low temperature side
giving half of the strength with respect to the peak value of
tan.delta. in the viscoelastic properties, while the "end point of
half value width of peak of tan.delta." means the point at the high
temperature side giving half of the strength with respect to the
peak value of tan.delta. in the viscoelastic properties.
[0105] From Table 1, when the total of the the acrylonitrile units
37 to 45 wt % and the acrylonitrile units and 1,3-butadiene units
is 93 wt % or more, the iodine value is 9 or less, and the half
value width of the peak of the loss tangent (tan.delta.) in the
viscoelastic properties is 5 to 20.degree. C. in range, it is
confirmed that the ordinary properties (tensile strength, 100%
tensile stress) and heat resistance are good and a superior oil
resistance can be realized (Examples 1 to 3).
[0106] On the other hand, when the ratio of the acrylonitrile units
was too high, the heat resistance was inferior (Comparative Example
1), while when the ratio of the acrylonitrile units was too low,
the oil resistance was inferior (Comparative Example 2). Further,
when the half value width of the peak of the loss tangent
(tan.delta.) in the viscoelastic properties was over 20.degree. C.,
the heat resistance was inferior (Comparative Example 3).
Furthermore, when the ratio of the butylacrylate units was 20 wt %
and the total of the acrylonitrile units and 1,3-butadiene units
was less than 93 wt %, the oil resistance was inferior (Comparative
Example 4).
* * * * *